The DNA virus SV40 represents a simple model system for examination of the phenomenon of eukaryotic cell transformation. A complete molecular characterization of the SV40 virion including those virus-coded proteins made in infected cells is essential for the identification of viral components which contribute to the transformation process. Considerable progress has been made toward determining the nucleotide sequence of the SV40 genome; until recently, however, analysis of viral gene product in this eukaryotic system has been limited by the lack of adequate methodology for chemical characterization of the primary structure of microgram amounts of proteins. The goals of this project are: 1) determination of the amino and carboxy-terminal sequences of the major SV40 specific proteins in order to establish the reading frame of the genome and correlate protein products with specific genetic regions; 2) microanalytic peptide mapping of the SV40 polypeptides to provide data on possible product-precursor relationships among the gene products; 3) extended development of selective chemical modification reactions for attachment of radioactive labels in a specific fashion for detection of minute amounts of material, thus allowing for peptide mapping and partial sequence analysis of SV40 proteins on a micro-scale; and, 4) eventual characterization, if possible, of altered viral proteins from temperature sensitive mutants of SV40 in order to confirm the assignment of specific viral functions. The major experimental approach for the proposed research involves microanalytic peptide mapping and protein sequence analysis. The results obtained and the methods employed will serve as a model for further study of virus-cell interactions in eukaryotic systems and will increase our understanding of the mechanism of virus-induced cell transformation.